I know vet assistants that make min wage and vet assistants that make 18 dollars and hour. It all depends on the clinic and the assistant. I don't know what the average is because wages vary so much depending on clinic and skill level.
I know vet assistants that are amazing and can do anything you ask ( X-rays, blood draws, IV Catheters, Jugular catheters, injections, etc etc etc) and most of it without asking. I also know vet assistants that are dog holders and thats it.